Question

Explain different types of car suspension systems.

Answer 1

Introduction

The automobile frame and body are mounted on the front and rear axle not directly but through the springs and shock absorbers. The assembly of parts, which perform the isolation of parts from the road shocks, may be in the forms of bounce, pitch and roll are called suspension system.

Functions of the suspension system

• It prevents the vehicle body and frame from road shocks.
• It gives the stability of the vehicle.
• It safeguards the passengers and goods from road shocks.
• It provides comfort.

There are two type of basic suspension system-

1. Independent suspension system.
2. Dependent suspension system.

Independent suspension system- The independent suspension system means any arrangement that connects road wheels to the frame in which raise or fall of the wheel has no direct effect on the other wheel. It eliminates wheel wobbling.

Advantages-

• It provides softer suspension.
• It reduces wheel wobbling.
• It reduces the tendency of fitting the wheel on one side due to road vibration.
• The movement of the spring on one wheel is not transmitted to the other wheel.  
• It promotes under steer which results in low un sprung weight.

Sprung Weight- It is the weight of all the parts supported by the spring including the weight of the spring.

Un sprung weight- It is the weight of all the parts between the spring and rod and the portion of spring weight itself.

Basic suspension movements-

• Bouncing- The vertical movement of the complete body.  
• Pitching- The rotating movement of all the parts between the spring and road and the portion of spring weight itself.
• Rolling- The movement about longitudinal axis produced by the centrifugal force during cornering.

Types of front Independent suspension system-

• Wishbone Type
• Vertical guide type
• Trailing Link Type.

Wishbone- In this type of suspension system coil springs are mostly used between the two suspension arms and are controlled with frame and at the open ends of the upper and lower wishbones which are connected to the chassis frame.  A coil spring is placed in between the lower suspension arm and frame.

Types of suspension springs-

• Steel Springs - a. Leaf Springs b. Coil Springs c. Torsion bar Springs.
• Rubber Springs- a. Compression Springs b. Progressive Springs.
• Plastic Springs
• Air Springs- a. Bellow Type b. Pestoon Type.

Leaf Springs- Leaf springs are formed by bending. They are made of long strips of steel. Each strip is named as Leaf. The long leaf is called Master Leaf, and it consists of eyes at its both ends. One end is fixed to the chassis frame, the other end is fixed to the shackle spring.

Types of Leaf Springs-

• Full – elliptic type
• Semi-elliptic type
• Three Quarter – elliptic type
• Transverse Spring type
• Helper Spring type

1. Full elliptic- The advantage of this type is the elimination of shackle and spring. The lubrication and wear frequently which are one of the main drawbacks of this type of springs.

2. Semi-elliptic-

3. Three – Quarter – elliptic type- This type is rarely used nowadays. It gives resistance but occupies more space than other types.

4. Transverse Type- This type of spring is arranged transversely across the car instead of longitudinal direction.

5. Helper Springs- The helper springs are used in heavy vehicles for the rear suspension. When vehicle fully loaded the main sp[ring as well as helper spring to come in action and absorb the road shocks. When the load of the vehicle is less the helper spring will not act and the mainspring only absorbs the road shocks.

Shock Absorber-

The shock absorber is a device that slows down the springing action of the suspension springs while also reducing the magnitude of vibrations.

If the suspension springs are rigid enough, they will not absorb road shocks efficiently, and if they are flexible enough, they will continue to vibrate for a long time even after the bump has passed. Therefore, the springing device must be compromised flexibility and stiffness a shock absorber needed in Automobile Suspension system.

Types of Shock Absorbers-

• Mechanical.
• . Hydraulic – a. Van type b. Piston – i )Single Acting ii). Double Acting c. Telescopic type.